The present invention relates to a seatbelt retractor that takes up a seatbelt so as to be windable and extractable, and particularly relates to the technical field of a seatbelt retractor having a belt load restricting mechanism (hereafter also referred to as an xe2x80x9cenergy absorbingxe2x80x9d or EA mechanism) which restricts the load placed on a seatbelt in the event of an emergency such as great vehicular deceleration occurring due to a collision or the like with the seatbelt being worn, by means of a torsion bar twisting and/or deforming.
Conventionally, seatbelt devices provided to vehicles such as automobiles restrain the passengers with seatbelts in the event of emergencies such as described above, thereby preventing passengers from flying out of their seats, thus protecting the passengers.
Such seatbelt devices have seatbelt retractors for taking up the seatbelt. The seatbelt retractor is arranged so that if the seatbelt is not being worn the seatbelt is taken up on the spool, and if the seatbelt is worn, the seatbelt is extracted and worn by the passenger. Further the seatbelt retractor is arranged such that a lock mechanism operates in the event of an emergency such as described above which obstructs the rotation of the spool in the direction of extracting the seatbelt, thereby obstructing extracting of the seatbelt. Thus, the seatbelt restrains and protects the passenger in a sure manner in the event of an emergency.
With seatbelt retractors in conventional seatbelt devices, a great vehicular deceleration occurs at the time of the seatbelt restraining and protecting the passengers in an emergency such as a collision of the vehicle or the like. In this situation, great inertia moves the passengers forwards. Accordingly, a great load is placed on the seatbelt and the passenger is subjected to a great shock force from the seatbelt. This shock force on the passenger is not particularly a problem, but preferably should be restricted, if possible, in different circumstances.
Accordingly, conventional seatbelt retractors have been developed with a torsion bar, so as to restrict the load placed upon the seatbelt in the event of an emergency when the seatbelt is being worn.
FIG. 4 is a cross-sectional diagram illustrating an example of a seatbelt retractor having such a torsion bar. In the Figure, reference numeral 1 denotes a seatbelt retractor, 2 denotes a frame in the shape of a box with one end open, 3 denotes a seatbelt, 4 denotes a spool which is rotatably supported by both side walls of the frame 2 in the shape of a box with one end open and which takes up the seatbelt 3, 5 denotes deceleration detecting means which detect greater vehicular deceleration generated in the event of an emergency such as described above and operates accordingly, 6 denotes a lock mechanism which operates due to the deceleration detecting means 5 and at least obstructs rotation of the spool 4 in the direction of extracting the seatbelt, 7 denotes a torsion bar which is movably fit and passed through the center of the spool 4 in the axial direction and which rotationally links the spool 4 and the lock mechanism 6 (this being equivalent to the seatbelt load restricting mechanism in the present invention), 8 denotes spring means for constantly pressing the spool 4 in the direction of taking up the seatbelt by the spring force of a spiral spring 9 via a bushing 10, 11 denotes a pretensioner which generates belt take-up torque by operating in the event of an emergency such as described above, and 12 is a bushing for transmitting the seatbelt take-up torque from the pretensioner 11 to the spool 4.
The lock mechanism 6 is provided with a locking base 14 (this being equivalent to the locking member in the present invention) which is capable of integrally rotating with a later-described first torque transmitting shaft 17 of the torsion bar 7 and holds a pawl 13 in a manner capable of locking, and the torsion bar 7 is provided with a lock gear 6a which normally integrally rotates with the torsion bar 7 but stops in the event of an emergency by the operation of the deceleration detecting means 5 and generates a relative rotational difference with the torsion bar 7 and engages the pawl 13 with inner teeth 19 on the side wall of the frame 2 so as to obstruct rotation of the locking base 14, that is the spool 4, in the direction of extracting the seatbelt. A male screw shaft portion 15 is formed to the locking base 14, and a nut-shaped stopper member 16 which integrally rotates with the spool 4 is screwed to this male screw shaft portion 15.
Also, a first torque transmitting portion 17 which engages the locking base 14 in a manner incapable of relative rotation is formed to the torsion bar 7, and a second torque transmitting portion 18 is formed which engages the spool 4 in a manner incapable of relative rotation.
Then, the spool 4 is constantly pressed by the spring force of the spring means 8 in the direction of taking up the seatbelt, via the bushing 10, torsion bar 7, second torque transmitting portion 18 of the torsion bar 7, and the bushing 12. Also, in the event of the pretensioner 11 operating, the belt take-up torque generated at the pretensioner 11 is transmitted to the spool 4 via the bushing 12, and thus the spool 4 takes up a predetermined 10 amount of the seatbelt 3.
With conventional seatbelt retractors 1 thus configured, the seatbelt 3 is completely taken up by the pressing force of the spring means 8 when the seatbelt is not being worn.
Extracting the seatbelt 3 at a normal speed for wearing causes the spool 4 to rotate in the seatbelt extracting direction, which allows the seatbelt 3 to be extracted smoothly. An unshown tongue slidably provided to the seatbelt 3 is inserted to and retained by a buckle fixed to the vehicle body, following which the portion of the seatbelt 3 which has been excessively extracted is taken up by the spool 4 by the pressing force of the spring means 8, and the seatbelt 3 is fit to the extent that the passenger does not feel too tight.
In the event of an emergency such as described above, the seatbelt take-up torque generated by the pretensioner 11 is transmitted to the spool 4, and the spool 4 takes up the seatbelt 3 by a predetermined amount, thereby securely restraining the passenger. On the other hand, under great vehicular deceleration generated in the event of an emergency, the deceleration detecting means 5 operates and the lock mechanism 6 operates. That is, the rotation of the lock gear 6a in the direction of extracting the seatbelt is obstructed by the operation of the deceleration detecting means 5, and the pawl 13 of the lock mechanism 6 rotates and engages the inner teeth 16 of the side wall of the frame 2. This obstructs the rotation of the locking base 14 in the direction of extracting the seatbelt, so the torsion bar 7 is twisted, and the spool 4 alone rotates in the direction of extracting the seatbelt relatively to the locking base 14. Subsequently, the spool 4 rotates in the direction of extracting the seatbelt while twisting the torsion bar 7, so the load placed on the seatbelt 3 is restricted by the twisting torque of this torsion bar 7, thus at least partially absorbing and alleviating the shock which the passenger is subjected to.
The relative rotation of the spool 4 as to the locking base 14 causes the stopper member 16 which integrally rotates with the spool 4 to relatively rotate as to the male screw shaft portion 15 to which it is screwed, and thus to move in the direction of the locking base 14. Then, at the point that the stopper member 16 abuts against the locking base 14, further rotation of the stopper member 16 is obstructed, so the rotation of the spool 4 is also obstructed, and twisting of the torsion bar 7 stops. Thus, the extracting of the seatbelt 3 is obstructed and the passenger is restrained by the seatbelt 3 in a more sure manner, while the maximum twisting of the torsion bar 7 is restricted and severing of the torsion bar 7 due to twisting is prevented.
Also, this conventional seatbelt retractor 1 is arranged so that the rocking base 14 of the lock mechanism 6 relatively rotates in the direction of extracting the seatbelt as to the lock gear 6a in the event that the seatbelt is rapidly extracted, and accordingly the pawl 13 of the lock mechanism 6 engages the inner teeth 19 of the side wall of the frame 2 in the same manner as above, thereby obstructing the rotation of the locking base 14, so the rotation of the spool 4 in the direction of extracting is obstructed via the torsion bar 7, and extracting of the seatbelt is obstructed.
Now, with such a conventional seatbelt retractor 1, a single restriction load is set by the torsion bar 7 alone, and the motion energy of the passenger is absorbed by only this one restriction load. However, in the event of restraining the passenger in cooperation with attached restraining means such as the above-described pretensioner 11 or other restraining/protecting means such as an unshown airbag, the restraining states of the passenger differ in various manners. Restraining the passenger in a more effective and appropriate manner is difficult with only one restriction load in such cases.
The present invention has been made in light of such, and it is an object thereof to provide a seatbelt retractor wherein the restriction load placed on the seatbelt can be flexibly set variously according to the particular emergency being experienced at the time.
In order to solve the above problems, the invention is a seatbelt retractor comprising at least: a spool for taking up a seatbelt; a lock mechanism having a locking member whereby rotation in the direction of extracting the seatbelt is obstructed in the event of an emergency; a torsion bar rotatably linking between the spool and the locking member, and capable of being twisting deformed; and a seatbelt load restricting mechanism for restricting the load placed upon the seatbelt by means of the torsion bar twisting deforming at the time that the rotation of the locking member in the direction of the seatbelt being extracted is obstructed and the spool rotates relative to the extracting direction of the seatbelt as to the locking member; wherein the seatbelt load restricting mechanism further changes the restriction load to be restricted for the seatbelt in multiple steps, in relation to the operation of at least one of a pretensioner and an airbag.
Also, the invention is characterized in that the restriction load has the maximum restriction load thereof set at the beginning following starting of operation of the seatbelt load restricting mechanism or set partway through the plurality of steps, and is set to the minimal restriction load from the twisting deformation of the torsion bar at the time of operation of at least one of the pretensioner and the airbag.
Further, the invention is characterized in that the stroke of the spool in the restriction load of each step at the time of relative rotation is set so as to be different in at least part of the steps.
Further, the invention is characterized in that the seatbelt load restricting mechanism further comprises, in addition to the above torsion bar, a second torsion bar that twist-deforms at the time of relative rotation of the spool, wherein the restriction load changes in steps by means of the second torsion bar breaking before the twisting deforming of the first torsion bar completing at the time of operation of at least one of the pretensioner and the airbag.
Further, the invention is characterized in that the seatbelt load restricting mechanism further comprises a restriction load switchover mechanism for performing switchover control of the portion where the second torsion bar twist-deforms in a predetermined number of steps, wherein the restriction load changes in steps by means of the portion of the second torsion bar, which twist-deforms to the end, breaking before the twisting deforming of the first torsion bar completing at the time of operation of at least one of the pretensioner and the airbag.
With the seatbelt retractor according to the present invention thus configured, the restriction load for restricting on the seatbelt changes in multiple steps, such as in relation to operation of at least one of the pretensioner and airbag, by the seatbelt load restricting mechanism. Accordingly, the restriction load placed on the seatbelt can be flexibly set variously according to the required state at the time of emergency. That is to say, for example, in the event of restraining the passenger in cooperation with at least one of the pretensioner and the airbag, the restriction load placed on the seatbelt can be adjusted more appropriately in accordance with the operation of at least one of the pretensioner and the airbag, by adjusting the restriction load placed n the seatbelt. For example, it may be desirable to increase the initial restriction of the passenger with the seatbelt at the initial period such as the period before the effects of the pretensioner and airbag occur, and then relieving the restriction of the passenger with the seatbelt at a later period such as the period wherein the effects of the pretensioner and airbag occur, for example.
Accordingly, the restriction load can be adjusted variously according to the restriction state of the passenger, thereby restraining the passenger in a more effective and appropriate manner.